Mattress



FIG. 1 is a front isometric view of a mattress.

FIG. 2 is a right side view of the mattress.

FIG. 3 is a left side view of the mattress.

FIG. 4 is a top view of the mattress.

FIG. 5 is a bottom view of the mattress.

FIG. 6 is a back view of the mattress; and,

FIG. 7 is a front view of the mattress.

The dashed lines represent structures that form no part of the claimed design. 

CLAIM The ornamental design for a mattress, as shown and described. 